The present invention relates to soldering apparatus, and in particular to a carriage for transporting printed circuit boards during an automated soldering operation.
EP 860 229 describes a carriage for raising, lowering and transporting a printed circuit board. Such carriages collect the board from a delivery station, transport the board into position above a solder bath and then raise and lower the board to dip component leads to solder them to the underside of the board. Such apparatus is well known in the art. In one type of prior art carriage, the board is held on the carriage by suction. Suckers descend down from the carriage and a suction is applied when the suckers are lowered on to the upper surface of the board. With this arrangement, a vacuum line must be carried by the carriage and the position of the suckers must be adjusted to suit different board designsxe2x80x94i.e. to attach to a suitable space on the board. In another arrangement, co-operating pincers hold the sides of the board. Each pincer has a cut-out and is pivoted inwards to trap the board edge in the cut-out. With this arrangement, pneumatic cylinders are carried on the carriage to pivot the pincers, and the position of the pincers must be adjusted to suit different board sizes.
In one aspect, the present invention provides a carriage in which opposed clamps each clamp an edge of the circuit board. The members of a clamp are biased to clamp the edges of the circuit board and co-operation of the clamp with a board delivery mechanism automatically separates the clamp members to allow entry and removal of the circuit board. Thus, the carriage need not carry vacuum lines or air lines.
The spacing between the clamps can be adjusted to accommodate different board widths. The clamps may be mounted on lead screws which are electrically rotated to adjust the spacing between the clamps to suit different width boards.
A clamp may comprise a first member having a flange on which the underside of the circuit board will rest, and a second member which is biased towards the flange to clamp the circuit board at its edge. This arrangement easily accomodates boards of different thickness as well as coping with a curved board.
In a particular arrangement, the carriage is lowered on to a track along which the circuit board can travel. The track has formations which cooperate with the clamp members to separate them as a clamp is lowered onto the track. A formation engages the second, upper clamp member to hold it as the carriage is lowered further to open apart the clamp members. A board is then delivered into the spaced apart clamps, sliding it lengthways between co-operating surfaces of the clamp members. As the carriage is raised, the upper clamp member moves back under the action of springs or the like to grip the circuit board.
If a clamp extends the full length of the circuit board it will have the added benefit of tending to straighten the edge of the board, removing some of the curvature which is a common problem when soldering circuit boards.